In time-division multiple access (TDMA) communication systems, each frame is an interval of T seconds, and each frame is divided into n discrete time slots. Thus, subscriber units can communicate with each other on a basis of non-overlapping transmission bursts. Since there is no overlap, a same carrier frequency may be assigned to all subscriber units using a same base site.
The TDMA technique is characterized by duration of the time frame and the time slot within the frame. Each time slot typically consists of a guard time, a preamble, and the information to be transmitted. Typically, the preamble contains system information such as synchronization, control and routing information. The guard time and the preamble generally depend on the organization of the system. The information to be transmitted occupies a predetermined number of bits.
Generally, any time slot in a frame is available for any subscriber unit. In such a system there is a need for a fair method of simultaneously allocating time slots between users as the number and location of available time slots within a frame changes.